XAML - How can I use a KeyBinding command to go to a new line in the textbox?

Question

I am simply trying to move to a new line when Return + Shift are pressed.

I got this much from a previous post on here:

<TextBox.InputBindings>
                <KeyBinding Key="Return" Modifiers="Shift" Command=" " />
</TextBox.InputBindings>

But I cannot find anywhere that explains how to accomplish the move to a new line within the textbox.

I cannot use the: AcceptsReturn="True" as I want return to trigger a button.

Answer 1

I found a nice way to do it without using an ICommand.

Simply added this PreviewKeyDown event onto the control in xaml:

PreviewKeyDown="MessageText_PreviewKeyDown"

And this is the C# behind:

private void MessageText_PreviewKeyDown(object sender, System.Windows.Input.KeyEventArgs e)
    {
        // Get the textbox
        var textbox = sender as TextBox;

        // Check if we have pressed enter
        if (e.Key == Key.Enter && Keyboard.Modifiers.HasFlag(ModifierKeys.Shift))
        {
            // Add a new line where cursor is
            var index = textbox.CaretIndex;

            // Insert a new line
            textbox.Text = textbox.Text.Insert(index, Environment.NewLine);

            // Shift the caret forward to the newline
            textbox.CaretIndex = index + Environment.NewLine.Length;

            // Mark this key as handled by us
            e.Handled = true;
        }
    }